general commercial - scotsman; ice review/291... · pdf file 2019-04-29 ·...

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  • General Commercial Service

    291-848

    Service Ports

    Compressor

    Suction Line

    Heat Exchanger Area

    Air Cooled Condenser

    Thermostatic Expansion ValveDischarge Line

    Water Inlet Valve

    Hot Gas Valve

    Service Ports

    Compressor

    Suction Line

    Heat Exchanger Area

    Air Cooled Condenser

    Evaporator

    Water Flow

    Thermatic Expansion Valve

    Discharge Line

  • 1

    General Commercial

    Service

    Segments

    • Cubers – – Prior (CM, CM3) and Prodigy – Undercounter cuber

    • Flakers – – Prior and Prodigy – Undercounter flaker – Ice maker-dispenser

    • Nugget ice dispensing

    • Hotel dispenser

    • Eclipse

    Recipe for Ice

    • Mix proper amounts of – Water – Refrigeration – Electricity

    • Too much or too little of any ingredient:

    – NO ICE!!!

    Cuber Control Type Review

    • All must terminate freeze, start and finish harvest. – Four freeze cycle termination methods:

    • Suction line temperature plus timer • Suction line temperature only • Reservoir water level • Direct sensing of water over ice bridge

    – Four harvest cycle termination methods: • Timed • Infrared light sensing ice • Suction line temperature only • Curtain switch

    Suction Line Temperature Method

    • Cube Size Thermostat – Normally Open, closes on temperature fall. Sensing suction line temperature. Contacts close at preset temperature to start a timer (mechanical or electronic) to finish the cycle

    – Many prior models, including CM, SCE170

    – Exception: CU0515 senses evaporator temperature – its closed contacts immediately trigger Harvest.

    Suction Line Temperature Method

    • Thermistor, attached to suction line

    – Resistance changes with temperature

    – Attainment of preset resistance starts electronic timer to finish the cycle

    • Applies to CU50

  • 2

    Water Level Method – CM3

    • Reservoir water level determines end of freeze

    • Sensed by float, stick and infrared sensor

    • As ice is made – Reservoir water level drops – Slot in the stick falls past the upper sensor – Triggers either

    • Refill or, • If all refills are complete, starts harvest.

    Water Level Sensor – Photo Eyes

    Lenses

    Back View

    Water Level

    Sensor

    Direct Sensing Method – Prodigy Cuber

    • Freeze continues until ice has increased in size to cause the water flowing over it to contact a sensor.

    • That contact triggers the controller to begin the harvest mode.

    Ice Thickness Sensor

    Contact with water makes circuit from controller to cabinet, terminating freeze

    Harvest Complete

    • Time only – timer advances a cam, microswitch on cam stops harvest.

    – CU50 and SCE170 have electronic timers in controller

    • Infrared sensors – harvesting ice falls between infrared emitter and detector, when no longer detected controller sets next cycle harvest time.

    • Evaporator temperature – CU0515. When the evaporator warms up to preset point, harvest stops.

    • Curtain switch – when ice pushes curtain away from switch, it triggers the controller to stop harvest.

    Timer Curtain Switch

    CU0515 Evaporator Thermostat

    Photo Eyes

    Freeze Termination Devices Curtain Switch - Prodigy

    • Switch is Open when curtain is Open – Open contacts trigger end of freeze

    • Indicator light is ON when switch is Open

    – Unused switch light is always on

  • 3

    Prodigy Cuber Sequence of Operation

    • Batch reservoir fill system on modular cubers – One fill per cycle – Fills until water sensor satisfied

    • Freezes until ice thickness sensor triggered by water contact

    • Harvests until curtain switch opens

    • Drains water and refills during part of harvest cycle

    CU1526/2026/3030 Water Level

    • Full reservoir system, controlled by float valve

    • Normal water level is 1” deep at left end of reservoir

    1 inch deep

    Prior Cuber Sequence of Operation

    • CM3 type – Batch reservoir fill system

    • Fills reservoir until water sensor satisfied + overflow time

    • Some models refill during freeze – CME456 – CME810 – CME1056 – CME1356/1656 – SCE275 – refills twice

    – Freezes until water drops enough to trigger harvest

    – Harvests until cube sensing quits – uses feedback from prior cycle

    Prior Cuber Sequence of Operation

    • SCE170 type – Full reservoir system – uses float

    valve – Freezes until cube size

    thermostat closes, starting electronic timer in the controller to finish freeze cycle

    – Harvests until curtain opens – Drains during harvest

    Prior Cuber Sequence of Operation

    • CM / DCE type – Batch reservoir fill system with

    inlet water solenoid valve – Fills reservoir continuously

    during harvest – Freezes until cube size

    control closes, starting timer – Timer finishes freeze and

    switches to harvest – Harvests until timer stops

    Cuber Diagnostics – No Ice

    • Unit off, nothing operating – Bin control keeping machine off (false bin full)

    • Thermostat • Curtain switch • Photo eyes • Ultrasonic

    – High pressure control open – Controller safety has stopped unit

    • Freeze or harvest cycle length – too short or too long • High or low discharge temperature • Lack of or too much water

    – Transformer failure

  • 4

    Cuber False Bin Full

    • Bin Thermostat – cold control – Used on CU50, CM and some CM3

    – CU or CM – opens on temperature fall – CM3 – closes on temperature fall – CM3 – connects to controller at #7

    • Standard on CME1056 and larger, optional on others

    – React to stop ice making at about 35oF. CM 3

    Cuber False Bin Full

    • Curtain Switch – Used on SCE170 and all Prodigy Cubers – Open switch shuts machine down

    • Curtain stays open – Stuck open – Magnet lost

    • Switch failure – Controller has indicator lights

    Cuber False Bin Full

    • Photo Eyes – Used in all CM3 including SCE275 – Photo eyes are infrared emitter and

    detector set – Scale on eyes will block light and

    cause Bin Full light to be ON all the time

    – Failed emitter or detector will also cause Bin Full light to be ON all the time

    – Controller unlikely to be the cause – No firm test available

    Dectectors

    Cuber False Bin Full

    • Ultrasonic – Sound wave timing measures ice level – Originally used on certain prior 1990s CMs – New design in 2007

    • Standard on EH222 • Optional thru Prodigy KVS kit

    • If adjusted too low, will stop ice making

    • If sensor socket is blocked, will stop ice making – Note – open curtain switch also triggers Bin Full light

    Cuber Diagnostics – No ice

    • Unit shut off on a safety 1. High discharge pressure 2. High discharge line temperature 3. High by pass line temperature 4. Long freeze time 5. Long harvest time 6. Short freeze time 7. Lack of refrigeration 8. Slow water fill

    1. High Discharge Pressure

    • All Remotes and Water Cooled Models

    • Some Air Cooled – Sensed by high pressure cut out switch – Cut out pressure varies: 400, 450 or 500 PSIG – Automatic reset – Does not power off controller

    • Causes – Hot ambient, poor ventilation – Fan motor failure, pressure switch failure – Water supply failure

  • 5

    2. High Discharge Temperature

    • CM3 and Prodigy – Sensed by thermistor on discharge line – Shuts unit off at 250oF.

    • Causes – High superheat at compressor

    • TXV starving plate • Low charge • High ambient

    – Thermistor out of calibration

    3. High By Pass Temperature

    • Prior CM models – Sensed by thermo disc

    temperature sensor by hot gas valve outlet

    – Sensor opens circuit at 140oF. Automatic reset

    – Cause: • Hot gas valve leaks

    thru during freeze

    4. Long Freeze Cycle

    • Applies to CM3 and Prodigy

    • Maximum times vary by product and model – CM3 – 31 to 50 minutes – Prodigy – 45 minutes for all but CU1526 (84)

    • Causes – Inlet water valve leaks thru during freeze – Purge valve leaks water down the drain – TXV superheat to high or too low – No refrigeration – any cause – Water pump failure – End of freeze not sensed by control system – Fans cycle (CM3) in warm ambient

    Long Freeze - Water Supply – Part of the Recipe

    • Too Much Water – Inlet water valve leak by symptoms:

    • Long freeze time – any model • Thick ice on CM3 models

    – Purge valve leak by • Thick ice on bottom of slab on Prodigy

    – Purge valve leak causes a refill • No ice at top row on CU1526/2026/3030

    – Causes float valve to open more as water drains out

    Long Freeze – No Refrigeration

    • Lost charge

    • Compressor off

    • Compressor will not pull down

    • Hot gas valve leaks by

    • TXV

    • Water supply off – water cooled

    • Headmaster bypassing or not used – remote

    Long Freeze: Hot Gas Valve Leaks